The present invention relates generally to structural members of the slotted angle type, and specifically to the provision of such a structural member having holes therein of an improved shape better to receive and hold an associated mounting stud therein.
Structural members have been provided heretofore with clover-leaf shaped holes wherein four identical cusps were arranged equiangularly therearound with concave surfaces joining adjacent cusps. In order to provide a tight joint when a headed stud was engaged in one of the clover-leaf holes, the shank of the stud was designed to rest upon the bottom radius of one of the concave surfaces, and in order to provide as tight a joint as possible, a snap lock was provided engaging in aligned apertures in the structural members being joined to hold the shank of the stud on the associated concave surface. Even when the resultant joint appeared to be tight, it was not tight enough to prevent racking between the upright and horizontal structural members. This racking resulted from the fact that the shank of the mounting stud had a slightly smaller radius than the radius of the bottom of the engaged concave surface and would slightly roll along the bottom radius of the engaged concave surface.
In yet other slotted angle designs for structural members, nuts and bolts were used to join the vertical and horizontal members in an effort to provide a tight joint therebetween. Racking still occurred because of the necessity to provide manufacturing tolerances, and the necessary rigidity was imparted to the resultant structure only by adding braces or other connections thereto.
Examplars of prior art structure of this general type are disclosed in U.S. Pat. No. 3,028,937 granted Apr. 10, 1962 to Edward W. Grabowski and Charles R. Johnson, U.S. Pat. No. 3,303,937 granted Feb. 14, 1967 to Kennedy McConnell, and U.S. Pat. No. 3,392,848 granted July 16, 1968 to Kennedy McConnell et al. The snap lock of the present application is disclosed in applicant's copending application for U.S. Pat. application Ser. No. 401,189 filed Sept. 27, 1973 now U.S. Pat. No. 3,905,712, issued Sept. 16, 1975, and the disclosure thereof is incorporated herein by reference.